Theory of structural relaxation in glass from the thermodynamics of irreversible processes

Impact of dynamic stretching exponent on the correlation between liquid fragility and nonexponentiality at the glass transition

The presence of large scatter in linear response data has cast doubt on the existence of an inverse correlation between liquid fragility and nonexponentiality, as originally proposed by Böhmeret al(1993J. Chem. Phys.994201). We present a model for the temperature dependence of the stretching exponent based on the Mauro-Yue-Ellison-Gupta-Allan model for supercooled liquid viscosity and discuss the factors impacting the relationship between fragility and the stretching exponent at the glass transition. The proposed model exhibits distinct advantages over previous models in terms of interpretability and limit behaviors for the temperature dependence.

Beyond the Average: Spatial and Temporal Fluctuations in Oxide Glass-Forming Systems

Atomic structure dictates the performance of all materials systems; the characteristic of disordered materials is the significance of spatial and temporal fluctuations on composition-structure-property-performance relationships. Glass has a disordered atomic arrangement, which induces localized distributions in physical properties that are conventionally defined by average values. Quantifying these statistical distributions (including variances, fluctuations, and heterogeneities) is necessary to describe the complexity of glass-forming systems. Only recently have rigorous theories been developed to predict heterogeneities to manipulate and optimize glass properties. This article provides a comprehensive review of experimental, computational, and theoretical approaches to characterize and demonstrate the effects of short-, medium-, and long-range statistical fluctuations on physical properties (e.g., thermodynamic, kinetic, mechanical, and optical) and processes (e.g., relaxation, crystallization, and phase separation), focusing primarily on commercially relevant oxide glasses. Rigorous investigations of fluctuations enable researchers to improve the fundamental understanding of the chemistry and physics governing glass-forming systems and optimize structure-property-performance relationships for next-generation technological applications of glass, including damage-resistant electronic displays, safer pharmaceutical vials to store and transport vaccines, and lower-attenuation fiber optics. We invite the reader to join us in exploring what can be discovered by going beyond the average.